Two Studies Reveal the Underlying Cause of Omicron's High Transmissibility

Two Studies Reveal the Underlying Cause of Omicron's High Transmissibility

Omicron has quickly overtaken its predecessors and has become the most dominant strain of COVID-19 to date. It has achieved this through its higher transmissibility levels, easily infecting exposed people regardless of how transient the encounter is. 

Initial thoughts on Omicron’s high transmissibility attributed it to higher viral loads, similar to the characteristics of the Delta variant. PCR tests during the reign of Delta revealed that the quantity of the virus in a single host was significantly more, enabling that person to spread the virus to others they come into contact with. 

But Omicron begs to differ. The results of two studies reveal that Omicron’s transmissibility prowess is not because of a high viral load. Instead, it is due to its immune evasion. The studies point out that Omicron’s mutations have the ability to evade immunity from vaccinations or past infections

The Studies on Omicron’s Viral Load and Immune Evasion

Infectious-disease specialist Yonatan Grad spearheaded the study on the underlying causes of Omicron’s higher transmissibility. His research focused on comparing the viral loads of COVID-19 variants using data from the National Basketball Association (NBA), which conducts frequent COVID-19 testing of its employees and basketball players. 

Grad collected positive PCR-test results from the NBA, which comprised infections linked to the Delta and Omicron strains. He found that those infected with Delta had a higher viral load than those who were infected with Omicron, concluding that viral load is not the main culprit behind Omicron’s higher levels of transmissibility. 

Grad’s research became a stepping stone for virologist Benjamin Meyer and his team, who probed deeper and measured viral RNA loads in swabs collected from almost 150 infected individuals. His research found that there was no significant difference between the viral loads of Delta and Omicron among vaccinated individuals.

The Same Studies Reveal Issues With Current Isolation Protocols

Along with measuring the viral load of the Delta and Omicron strains, Grad and Meyer’s respective studies also revealed how long Delta- and Omicron-positive individuals remain infectious. 

Grad’s study showed that half of his sample had viral loads high enough to be infectious five days after testing positive. Meyer, on the other hand, found that the test results of vaccinated individuals infected with Delta still detected viral RNA five days after initial test results. 

These findings don’t coincide with the current CDC guidelines on isolation periods, which only require infected individuals to self-isolate for five days after testing positive or presenting initial symptoms. After which, they can end their isolation but continue to wear masks for another five days. 

Given that Grad and Meyer’s studies revealed possible infectiousness five days after testing positive with Delta and Omicron, they recommend that negative COVID-19 tests be required to ensure the non-detection of viral loads before the isolation period can end.


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